Double-walled carbon nanotubes promote ASC speck formation and inflammasome activation in vascular endothelial cells

Carbon nanotubes (CNTs) are important industrial nanomaterials, yet their manufacture presents potential risks for respiratory exposure among workers. CNTs have a high aspect ratio, which raises concerns that they may cause toxicity similar to that of asbestos. Asbestos is known to activate the NLR family pyrin domain containing 3: NLRP3, a key component of inflammasome. We hypothesized that CNTs promote atherosclerosis by enhancing inflammatory response triggered by inflammasome activation. Treatment of human umbilical vein endothelial cells (HUVECs) with two types of double-walled CNTs (DWCNT; NC2150 and NC2100) resulted in a significant increase in the levels of cytoplasmic agglutination of adapter apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (ASC) and the levels of phosphorylated ASC and interleukin (IL)-1β. In addition, DWCNT upregulated the expression of adhesion molecule ICAM-1. Consistent with these in vitro findings, apolipoprotein E-deficient (Apoe^-/-) mice exposed to high-dose DWCNT showed a significant increase in aortic plaque area, and upregulation of NLRP3 and IL-1β as well as that of adhesion molecule (ICAM-1) and chemokine (MCP-1) in the thoracic aorta. The results of our in vitro and in vivo studies suggested that exposure to high-dose DWCNT induced atherosclerogenesis by enhancing inflammasome-driven inflammatory responses with ASC speck formation.